TOKYO (AP) -- As negotiations falter, President Barack Obama is rejecting suggestions that an Asia-Pacific trade deal is in danger and says the U.S. and Japan must take bold steps to overcome differences that are threatening completion of the cornerstone of his strategic rebalance to the region.

Talks broke off hours after Obama spoke and were not expected to resume soon.

Standing alongside Japanese Prime Minister Shinzo Abe, Obama also affirmed that the U.S. will defend its Asian ally in a potential confrontation with China over a set of disputed islands. At the same time, he called on both parties to peacefully resolve the long-running dispute that has heightened tensions between the two countries.

On the first full day of a four-nation visit to Asia, Obama called for the U.S. and Japan to resolve disagreements promptly over access to agriculture and automobile markets, issues that are hindering completion of the Trans-Pacific Partnership. The deal, involving 12 nations overall, is a key component of Obama's efforts to assert U.S. influence in Asia in the face of China's ascendancy in the region.

"Now is the time for bold steps that are needed to reach a comprehensive agreement, and I continue to believe we can get this done," Obama said at a joint news conference with Abe at the Akasaka Palace. "All of us have to move out of our comfort zones and not just expect that we're going to get access to somebody else's market without providing access to our own. And it means that we have to sometimes push our constituencies beyond their current comfort levels because ultimately it's going to deliver a greater good for all people."

That was also a nod to the strong opposition Obama faces at home to the TPP, including from organized labor groups who fear such a deal with leave U.S. workers vulnerable to competition from counterparts in other countries who earn substantially less. Obama's fellow Democrats in Congress also oppose granting him authority that would make it harder for lawmakers to change the trade pact. Business groups strongly back the deal, saying it would create jobs and open new markets to U.S. goods.

Akira Amari, the top Japanese negotiator for the TPP talks, said Thursday evening that the talks with chief U.S. trade negotiator Michael Froman "have stopped for now" and were not expected to resume "straight away," meaning there will be no breakthrough on the agreement during Obama's visit.

"The old issues still remain," said a grim-looking Amari.

The U.S. had no immediate comment on the status of the talks following Thursday's negotiations.

In a show of solidarity with Abe, Obama affirmed that a treaty between their countries would obligate the U.S. to defend Tokyo in a potential clash with Beijing over islands in the East China Sea, called Senkaku by Japan and Diaoyu by China. Obama said the U.S. takes no position on whether the islands are ultimately in the dominion of China or Japan, but he noted that Japan historically has administered the islands.

"We do not believe that they should be subject to change unilaterally," Obama said. "What is a consistent part of the alliance is that the treaty covers all territories administered by Japan."

Although Obama has sought to avoid getting dragged in to territorial disputes an ocean away, Japan and other U.S. allies see them through the broader lens of China's growing influence in Asia.

Beijing is watching closely for signs that U.S. is seeking to limit China's rise, while smaller nations want reassurance from Obama that his push to increase U.S. influence in Asia hasn't petered out. China reacted angrily to Obama's very public statement of support for Japan, with a Foreign Ministry spokesman saying "we are firmly opposed to the inclusion" of the islands in the U.S.-Japan security treaty.

Obama's advisers insist the trip -- and the White House's broader Asia policy -- is not designed to counter China's growing power, and they say the president is not asking Asian nations to choose between allegiance to Washington or Beijing.

"We want to continue to encourage the peaceful rise of China," Obama said.

Addressing another source of tension in the region, Obama said he's not optimistic North Korea will soon change its provocative behavior. But he said he's confident that by working with Japan, South Korea and others -- especially China -- the U.S. can apply more pressure so that "at some juncture they end up taking a different course."

Underscoring his concerns about North Korea's behavior, Obama met after the news conference relatives of Japanese citizens that the White House said were abducted years ago by North Korea. Obama recommitted to working with Japan to address the North's "deplorable treatment of its own people," the White House said.

Obama began Thursday at the Imperial Palace, with a formal greeting by Emperor Akihito, and was ending his day there at a state dinner in his honor.

He also spent time taking in some of what Tokyo has to offer, including a visit to the Meiji Shrine, which honors the emperor whose reign saw Japan emerge from more than two centuries of isolation to become a world power. Obama also gave a pep talk to science students at the National Museum of Emerging Science and Innovation, also called Miraikan, and played around with ASIMO, a humanoid robot made by Honda. ASIMO ran across a room and kicked a soccer ball to the president.

"Welcome to Miraikan, Mr. President. It is a pleasure to meet you," ASIMO said in true robot-like cadence.

The president will also visit South Korea, Malaysia and the Philippines, stops that serve as a do-over after he canceled a visit to Asia last fall because of the U.S. government shutdown.